There is an ongoing unresolved need for polymer compositions having improved rheological and aesthetic properties in aqueous media.
Synthetic rheology modifier polymers typically fall within one of four categories: alkali-soluble emulsion (“ASE”) polymers, hydrophobically modified alkali-soluble emulsion (“HASE”) polymers, hydrophobically modified ethoxylated urethane (“HEUR”) polymers, and hydrophobically modified nonionic polyol (“HNP”) polymers. HASE is typically a low viscosity emulsion at low pHs. To increase viscosity, the emulsion is neutralized to pH above 7, preferably above 8. When it is neutralized, HASE swells and viscosifies. The hydrophobic modifications, for example, the terpene alkoxylate components acting like stickers and the acrylate-based extended hydrophilic brushes are responsible for creating the swollen 3-D structure as viscous gels. FIG. 1 shows an idealized diagram of the swelling of HASE polymer at alkaline pH. In particular FIG. 1 shows a low viscosity emulsion 2 containing a HASE latex particle 4 reacted with base forms a viscous solution 6 having a HASE 3D Network 8.
HASE and ASE polymers, see, for example those described in, U.S. Pat. No. 3,035,004, U.S. Pat. No. 5,292,843, U.S. Pat. No. 6,897,253, U.S. Pat. No. 7,288,616, U.S. Pat. No. 7,378,479, and US Patent Publication No. 2006/0270563, have each been widely used as rheology modifiers in aqueous systems.
However, there is a continuing need to compositions with improved resistance to high salt concentrations, and improved resistance to the potentially high temperatures involved in some of their uses.
For example, there is a need for improved polymer compositions for use in a variety of methods for recovering natural gas and crude oil from subterranean formations. One such technique is hydraulic fracturing of the subterranean formation conducted to increase oil and/or gas production. Fracturing is caused by injecting a viscous fracturing fluid or a foam at a high pressure (hereinafter injection pressure) into the well to form a fracture. As the fracture is formed, the particulate material, referred to as a “propping agent” or “proppant” is placed in the formation to maintain the fracture in a propped condition when the injection pressure is released. Coated and/or uncoated particles are often used as proppants to keep open fractures imposed by hydraulic fracturing upon a subterranean formation, e.g., an oil or gas bearing strata. Particles typically used to prop fractures generally comprise sand or sintered ceramic particles as the fracture forms, the proppants are carried into the fracture by suspending them in additional fluid or foam to fill the fracture with a slurry of proppant in the fluid or foam. Upon release of the pressure, the proppants form a pack that serves to hold open the fractures. Thus, the proppants increase production of oil and/or gas by providing a conductive channel in the formation. The degree of stimulation afforded by the hydraulic fracture treatment is largely dependent upon formation parameters, the fracture's permeability and the fracture's propped width.
In oilfield fracturing, there is a need for a proppant carrier that is a viscoelastic medium that can prevent proppants or sand from settling while being position in the fractures. Two common chemistries are in the market: natural polymers (guars, etc), and visco-elastic surfactant systems (VES). Guar and VES are existing proppant carriers used in fracturing fluids. Guar is a polysaccharide and is being used for many decades. VES in fracturing has been used for about a decade. Visco-Elastic Surfactant (VES) fluids are polymer-free fluids that generate viscosities suitable for fracturing operations without the use of polymer additives. Viscosity of a VES fluid is created by self-assembly of surfactant molecules in an aqueous solution. The use of synthetic polymers, like polyacrylamides, polyacrylates and other copolymers by themselves or with combination with VES or guar and/or the use of various crosslinkers is more recent.
US Patent Application Publication No. 2009/0145607 to Li et al entitled High Temperature Fracturing Fluids and Method of Use discloses a treatment fluid for treating a subterranean formation comprising: an aqueous solution of a polysaccharide, a polyacrylamide, a crosslinking agent, and less than 0.1% by weight of any clay component, wherein the polyacrylamide is present in an amount of from about 0.01 percent to about 1 percent by weight of the fluid. In an embodiment the polysaccharide is selected from carboxymethylhydroxypropyl guar (CMHPG), hydroxypropyl guar, guar and combinations of these.
US Patent Application Publication No. 2006/0270563 to Yang et al. discloses a HASE copolymer also known as a pH responsive polymer. Yang et al also discloses a hydraulic fracturing composition comprising water and this pH responsive polymer and a proppant.
A number of polymer-free aqueous fracturing fluids are based on viscoelastic surfactants. The principal advantages of viscoelastic surfactant fluids are ease of preparation, minimal formation damage and high retained permeability in the proppant pack. Viscoelastic surfactant fluids are disclosed, for example, in U.S. Pat. Nos. 4,615,825, 4,725,372, 4,735,731, CA-1298697, U.S. Pat. Nos. 5,551,516, 5,964,295, 5,979,555 and 6,232,274. One well-known polymer-free aqueous fracturing fluid comprising a viscoelastic surfactant, which has been commercialized by the company group Schlumberger under the trademark ClearFRAC, and a mixture of a quaternary ammonium salt, the N-erucyl-N,N-bis(2-hydroxyethyl)-N-methyl ammonium chloride, with isopropanol and brine, the brine preferably including 3% by weight of ammonium chloride and 4% by weight of potassium chloride.
Published PCT application WO 87/01758 entitled “Hydraulic Fracturing Process and Compositions” discloses fracturing processes which use aqueous hydraulic fracturing fluids. The fluids comprise: (a) an aqueous medium, and (b) a thickening amount of a thickener composition comprising (i) a water-soluble or water-dispersible interpolymer having pendant hydrophobic groups chemically bonded thereto, (ii) a nonionic surfactant having a hydrophobic group(s) that is capable of associating with the hydrophobic groups on said organic polymer, and (iii) a water-soluble electrolyte. Additionally, the fluids preferably contain a stabilizing amount of a thiosulfate salt. As an example, an interpolymer of acrylamide and dodecyl acrylate was used in combination with a nonionic surfactant (HLB of from 10 to 14) to thicken a dilute aqueous solution of KCl and sodium thiosulfate; the aqueous solution had excellent properties for use as a high temperature hydraulic fracturing fluid.
U.S. Pat. No. 4,432,881 entitled “Water-Dispersible Hydrophobic Thickening Agent” discloses an aqueous liquid medium having increased low shear viscosity as provided by dispersing into the aqueous medium (1) a water-soluble polymer having pendant hydrophobic groups, e.g., an acrylamide dodecyl acrylate copolymer, and (2) a water-dispersible surfactant, e.g., sodium oleate, or dodecyl polyethyleneoxy glycol monoether. The thickened aqueous medium is suitably employed in applications requiring viscous liquids which retain their viscosity when subjected to shear, heat or high electrolyte (salt) concentrations. Such applications include uses in oil recovery processes, as fluid mobility control agents, fracturing fluids and drilling muds, as well as hydraulic fluids and lubricants in many applications.
Also, U.S. Pat. No. 5,566,760 entitled “Method of Using a Foamed Fracturing Fluid” discloses a fracturing fluid comprising surfactants and hydrophobically-modified polymers. In these fluids, surfactant molecules form the interface between gas bubbles and the polymer molecules that form a polymeric network similar to those of the pure polymeric fluids. Still, there is no mention of viscoelastic surfactants or of the responsiveness of the fluids to hydrocarbons.
In addition to fracturing, other techniques may be employed to further improve hydrocarbon recovery from subterranean formations. There is also a need for improved treatment fluids for “enhanced oil recovery” techniques for treating subterranean formations after the oil has been produced from a formation by pressure depletion (primary recover). In pressure depletion, the differential pressure between the formation and a production well or wells forces the oil contained within the formation toward a production well where it can be recovered. Typically, up to about 35 percent of the oil initially contained in a formation can be recovered using pressure depletion. This leaves a large quantity of oil within the formation. Additionally, some formations contain oil which is too viscous to be efficiently recovered from the formation using pressure depletion methods. Because of the need to recover a larger percentage of the oil from a formation, methods have been developed to recover oil which could not be recovered using only pressure depletion techniques or secondary recovery techniques. These methods are typically referred to as “enhanced oil recovery techniques” (EOR).
U.S. Pat. No. 7,727,937 to Pauls et al, incorporated herein by reference in its entirety discloses acidic treatment fluids used in industrial and/or subterranean operations, and more particularly, acidic treatment fluids comprising clarified xanthan gelling agents, and methods of use in industrial and/or subterranean operations, are provided. In one embodiment, the acidic treatment fluids comprise an aqueous base fluid, an acid, and a gelling agent comprising clarified xanthan.
U.S. Pat. No. 7,789,160 to Hough et al, incorporated herein by reference in its entirety discloses an aqueous fluid useful for the recovery of crude oil from a subterranean formation, which includes a composition including a mixture of water, a water soluble block copolymer, an inorganic salt and at least one member of the group of a nonionic surfactant having an HLB of less than 12, and methods for using same.
U.S. Patent Application Publication 2003/0134751 discloses addition of polymers to a viscoelastic surfactant base system allows adjusting the rheological properties of the base fluid. The polymer can perform different functions (breaker, viscosity enhancer, or viscosity recovery enhancer) depending upon its molecular weight and concentration in the fluid. The methods and compositions are presented for adjusting the viscosity of viscoelastic surfactant fluids based on anionic, cationic, nonionic and zwitterionic surfactants.
U.S. Patent Application Publication 2005/0107503 A1 describes an aqueous viscoelastic fracturing fluid for use in the recovery of hydrocarbons. The fluid comprises a viscoelastic surfactant and a hydrophobically modified polymer. The viscoelastic surfactant is usually ionic. It may be cationic, anionic or zwitterionic depending on the charge of its head group.
Among the more promising of the methods being used today is an enhanced oil recovery process referred to as a surfactant flood. An aqueous fluid containing surfactant is injected into an oil rich formation to displace oil from the formation and the displaced oil is then recovered.
Another promising method being used today is an enhanced oil recovery process referred to as chemical flooding which generally covers the use of polymer and/or surfactant slugs. In polymer flooding, a polymer solution is injected to displace oil toward producing wells. The polymer solution is designed to develop a favorable mobility ratio between the injected polymer solution and the oil/water bank being displaced ahead of the polymer. However, the use of polymer is not always satisfactory as many polymer solutions are sensitive to brine type and concentration which can affect the apparent viscosity of the solution. In surfactant flooding, an aqueous solution containing surfactant is injected into the oil rich formation. Residual oil drops are deformed as a result of low Interfacial Tension provided by surfactant solution and drops are displaced through the pore throats and displaced oil is the recovered.
It would be desirable to provide high temperature stable fracturing fluids and EOR fluids for subterranean formations, such as natural gas and/or oil field.
Also there is a need to enhance viscosity to improve personal care compositions and cleaning compositions for home and industry. In home and personal care there is a need for stable combinations of polyanionic and cationic polymers for personal care products 2-in-1 shampoo and conditioner. For home care it is in detergent and softener in one.